There exist in technology today numerous types of energy collection conversion systems which heat and cool homes and other buildings. Each of these existing systems has disadvantages which make it somewhat undesirable in light of the present energy demand and fuel shortage.
For example, the most prominent of systems are fuel combustion systems. These systems have disadvantages in that they require fuel which is expensive and in uncertain supply. Fuel combustion systems require fuel for combustion and also an additional amount of energy to circulate the heat transfer medium. Also, the waste products of combustion must be disposed of resulting in undesired air pollution and loss of produced energy. Moreover, the heating and cooling modes of a typical modern system usually require two separate heat exchange systems to operate with one air circulation system.
Solar heat systems can collect heat feasibly only during daylight hours of high radiation days and storage facilities are needed to retain contained heat between periods of collection and use/demand. Additional heat circulation apparatus is required to circulate the heat stored from the solar heat collector throughout the areas to be heated.
Heat pump systems have similar disadvantages in that additional energy input is required for both the heat collection function and for circulation of the heat transfer medium. If the external atmosphere is used as a heat source, efficiency decreases as the external temperature decreases, so that supplemental heat from fuel or electrical systems may be required. The thermal cycling of the heat transfer medium requires additional equipment which must be purchased and maintained.
Environmental kinetic energy systems such as windmills, water power, etc. are not always practical as an energy source and the storage of energy accumulated is both difficult and expensive. Machinery for subsequently making use of the energy is required and requires maintenance and replacement.